Special To Pipeline News
A 55-mile stretch of Dominion’s Appalachian Gateway Project being constructed through western Pennsylvania will help supply Mid-Atlantic and northeastern states with a much-needed source of natural gas.
Brownsville, WI-based Michels Pipeline Construction is contracted to build the 24-inch X70 transmission pipeline, scheduled to go into operation in September.
As work began in August 2011, Michels was faced with several challenges: a varying and treacherous terrain, narrow stretches of right-of-way that bordered residential areas, and a wet fall that consistently muddied the site. The company used a combination of truck-mounted welders and welding sleds to weld the pipe, depending on weather conditions and width of the right-of-way.
The project marked one of the most concentrated uses of Miller’s new Big Blue® 350 PipePro® diesel engine-driven welder generators, designed specifically for transmission pipeline construction. Michels rented several units for the sleds and many of Local 798 pipeline welders hired by Michels outfitted their trucks with the new machine. Engine-driven welding technology has evolved to where machines are providing greater functionality and performance in a smaller fuel-efficient package.
“It’s a crisp arc that will weld a pipe and it bonds real quick,” said Floyd East, a welder with Michels. “It’s quieter, smoother, lighter, has more power. It’s 325 amps at 100% duty cycle, and it only weighs 1,018 pounds vs. (other machines) that are 1,400 pounds and 200-amp duty cycle, and they don’t have wire features or Lift-Arc TIG. There’s a whole lot more options on these, including 220- and 110-plug-ins. It’s cheaper on fuel.”
Wall thickness of the X70 pipe used in this project varies depending on where the pipe is being laid. The mainline consists of both .375- and .438-inch wall thicknesses, while residential areas and road crossings feature .500-inch-thick pipe. Each joint is welded in three steps, with an assembly line-like procession of trucks and machines making its way down the pipe. The first crew runs a root pass; the second crew welds a hot pass; and a third crew welds fillers and a cap pass. Each pass is completed by two welders who simultaneously weld from the top of the pipe to the bottom of the pipe directly opposite of one another.
This entire stretch of the pipeline is being welded with the cellulosic stick electrode process. E6010 electrodes are being used on the root pass, and E8010-G electrodes are used for all fill and cap passes. While these cellulosic electrodes are specified for this job, they can create an erratic arc and large amounts of spatter, depending on how they are used. Welders on this project report that the PipePro has helped reduce those problems through advanced arc controls. The machine’s Hot Start™ function provides positive stick electrode starts while its adjustable arc control automatically adjusts DIG, which determines how much amperage varies with arc length.
“It’s more controllable, more stable,” said Tim Gintz, welder foreman, Michels. “It allows you to put (the bead) where you want it. It cuts through the metal better (than older machines) and it flows much better — you don’t have to wait on it. ”
Engine-driven welding generators of the past have also been notorious for being affected by temperature and other extreme conditions, often presenting varying arc characteristics throughout the day or week. The design of the PipePro, combined with the fact that it is rated at 104 degrees Fahrenheit, helps ensure machine performance no matter the time of day or weather conditions.
“It’s very consistent from the time you start in the morning to the afternoon in terms of amperage and voltage,” said Michels’ welder Dale Kennedy. “The arc performance is consistent all day long.”
The machine also goes through rigorous testing for the extreme conditions found in pipeline applications: airborne dust and sand, humidity and corrosion, temperature extremes, jobsite abuse and continuous heavy operation. East, who has had his machine for more than a year, reports no problems to date.
One factor for an independent rig owner or a pipeline contractor when specifying a piece of equipment is fuel costs. When Miller designed the new PipePro, it incorporated a new EPA Tier 4 Compliant Mitsubishi S4L2 4-cylinder engine that operates at 1,850 RPM instead of 3,600 RPM. This helps reduce fuel use by up to 50% compared to other machines on the market and by 20% compared to Miller’s previous machine in this size class. When matched head-to-head, the fuel savings are evident.
“We’re working on sleds, and the other machine uses 2.5 more gallons of fuel per day,” said Kennedy. “We’ve measured it several times while working them hard.”
If East works an average of 260 days, that adds up to between $1,560 and $2,080 in fuel savings annually. It also reduces hassles on site because it reduces the number of trips a fuel truck has to make to fill up a machine (contractors are not allowed to keep diesel cans on their trucks). The lower RPM also provides another crucial benefit: it lowers sound levels by about 40%.
“Noise of any kind is detrimental,” said Gintz. “It’s a safety factor. (Now) people can hear you even though you have a hood down.”
Pipeline welders must fit every tool they need for a job onto their trucks. The most common trucks pipeliners use for rigs feature dual wheel rear-axles, which are typically necessary to carry that weight. They also invite more scrutiny from DOT authorities in terms of weight limits, which have driven some contractors to switch to three-quarter-ton trucks. Considerably smaller machines like the PipePro — which weighs 1,018 lbs. — have helped contractors reduce weight and better optimize space on their trucks with a smaller footprint.
Every pipeline welder has a helper, and that helper is typically anchored to a corded remote box while the welder is making a weld. Part of the helper’s job is remote management, including rolling and unrolling cord.
The PipePro is compatible with Miller’s new wireless remote technology, which eliminates hassles and potential malfunctions associated with corded remotes, and features a digital display that tells the helper what the machine is set at. With a range of 300 feet from the machine, wireless remotes provide welders and their helpers an efficient way to dial the machine in accurately and ensure quality at the point of use.
The machine offers other key benefits: 12,000 watts of peak single-phase power (10,000 watts continuous) provides more than enough power to run jobsite tools such as grinders. Meter maintenance displays help simplify maintenance. A standard LINE-X® cover provides superior impact, corrosion and abrasion protection. As pipelines throughout North America begin switching to high-strength steels and move away from cellulosic stick electrodes, contractors will be expected to utilize low hydrogen processes. Flux Cored welding is the most viable option and the Big Blue 350 Pipe Welding System is optimized for welding these wires.